(a) Field of the Invention
The present invention relates to a decoding method. More particularly, the present invention relates to a decoding method and device using dynamic scheduling for low density parity check codes.
(b) Description of the Related Art
In order to satisfy the high data rate of the current next generation mobile communication system, studies on a encoding method having efficient performance with a short length and a decoding method with fast convergence rates have progressed, and particularly, various decoding methods for low density parity check (LDPC) codes have been aggressively studied.
Regarding the LDPC codes decoding method, a check node or a variable node receives a message from the neighboring node to update it, returns the updated message to the corresponding neighboring nodes, and then repeats this process to correct the errors and decode the message. An output message of the variable node or the check node represents a function of messages coming into the node except the line for transmitting the message, that is, the message coming from the edge.
The method for determining the order of updating the messages is called scheduling, and the scheduling decoding method is classified as a static scheduling decoding method for sequentially updating the messages according to a fixed order and a dynamic scheduling decoding method for dynamically updating the messages.
The static scheduling decoding method is classified as a shuffled belief propagation (SBP) method and a layered belief propagation (LBP) method depending on the update in the variable node direction or the update in the check node direction. After introduction of the SBP and the LBP, various modified types of schemes have been researched.
The existing scheduling decoding method is also called a residual belief propagation (RBP) method, and it initially updates the message with the greatest variation between before and after the update from among the messages transmitted from the check node to the variable node.
The fact that a difference of the message value between before the update and after the update is near 0 indicates that the message is almost converged, and the fact that a difference of the message value between before the update and after the update is great indicates that the message is not converged. Therefore, the convergence rate of the dynamic scheduling decoding method for updating the message that is not converged in advance to other ones is much faster than the decoding convergence rate of the static scheduling decoding method such as the SBP and the LBP for updating the message according to a fixed order. Also, since the dynamic scheduling decoding method can efficiently solve a trapping set error, it outperforms the static scheduling decoding method.
However, since the existing dynamic scheduling decoding method for LDPC codes performs scheduling in the order starting from the great difference between before the update and after the update of the message transmitted from the check node to the variable node, the decoding convergence rate becomes faster, but the reliability of the message transmitted from the check node to the variable node is worsened because it is based on only one check equation. In detail, the same method may greatly mistakenly determine the message, but the erroneously determined message can be updated in advance to cause a new error.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.